In the application field of optoelectronics, such as optical devices, displays and optical information transmission, intensive research and development of transparent materials have been made and the utilization of the transparent materials has been studied. In the above application field, a wavelength ranging from 350 to 500 nm tends to be positively utilized from the viewpoints of high energy density and efficiency.
As high-performance polymers for electronic equipments, polyimide resins are generally known. In particular, from the viewpoint of good heat resistance, aromatic polyimide resins have been conventionally used. However, the aromatic polyimide resins absorb light in the above wavelength range and their use as a transparent material is limited. Therefore, the development of non-aromatic polyimide resins having high heat resistance comes to be demanded. In addition, heat-resistant transparent materials to be applied to the field of optoelectronics are required to be good not only in mechanical properties, such as tensile strength and elongation at break, but also in properties, such as adhesion to silicon substrates or glass substrates and solubility in general-purpose solvents.
To obtain polyimide resins having the above-mentioned properties, it has been studied to use a silicon-containing alicyclic tetracarboxylic dianhydride as a constituting unit of the polyimide resins.
For example, Patent Document 1 discloses a polyimide resin produced using a tetracarboxylic dianhydride represented by formula (4):
which is synthesized from 5-norbornene-2,3-dicarboxylic anhydride and a dimethylsiloxane terminated at each end with a hydrosilyl group.
Non-Patent Document 1 discloses a polyimide resin produced using a tetracarboxylic dianhydride represented by formula (5):
which is synthesized from 5-norbornene-endo-2,3-dicarboxylic anhydride and hexamethyltrisiloxane. It is reported that this polyimide resin is transparent to light with a wavelength of 350 nm or longer.
Non-Patent Document 2 discloses a polyimide resin which is produced by a very specific polymerization method (disiloxane equilibration reaction). The polyimide resin is terminated at each end with a pentamethyldisiloxane structure and has repeating units derived from a tetracarboxylic dianhydride represented by formula (6):
